Pressure relief mechanism



Aug. 22, 195o v WOLFE 2,519,990

PRESSURE RELIEF MECHANISM Filed April 26, 1947 JNVENToR. cfm/H1355 Kil/MFE,

Patented Aug. 22, 1950 UNITED STATES PATENT OFFICE Charles Wolfe, Indianapolis, Ind., assignor to E. IC. Atkins and Company, Indianapolis, Ind.,

a corporation of Indiana Application April 26, 1947, Serial No. 744,274

l2 Claims. 1

The high speed rotation of parts within a sub. stantially fluid-tight, lubricant-containing gear box results, at times, in building up a fluid pressure within such box; and the pressure differential between the inside and the outside of the box will sometimes cause lubricant to escape. In many installations, it is substantially essential to prevent such escape of lubricant, either because the equipment is used in an environment wherein escaping lubricant might contaminate the work or injure parts of the same machine which are subject to damage by contact with oil, or because the equipment is used under circumstances such that frequent replenishment of the lubricant supply is not feasible, or for other reasons..

It is desirable, therefore, to provide means for overcoming the tendency of lubricant to escape from the gear housing; and I propose to accomplish that result by providing means for relieving the pressure so built up by permitting the escape of air from the interior of the gear box, during operation of the equipment only, and without permitting the escape of lubricant through the air escape path. It is the primary object of the present invention, then, to provide,in combination with a substantially fluid-tight housing in which a rotating part is journalled, means for permitting the escape of gas from the interior of such a housing, only during operation of the equipment, and without permitting the escape of liquid through the gas-escape path. A further object of the invention is to provide simple, inexpensive, automatic means for accomplishing the above results. A still further object of the invention is to provide, in the described equipment, a valve controlled escape passage so constructed and arranged that the passage is always closed except when the parts are rotating, and that the passage is opened, during rotation of the parts, by the effect of centrifugal force upon a simple, ball check valve, normally spring pressed to its seat. A still further object of theinvention is to arrange the relief unit in such a fashion that the gas-escape passage is substantially radial with respect to the axis lof rotation of the part with which it is associated, so that the effect of centrifugal force will positively prevent iiow of liquid out from the interior of the housing through such path. A further object of the invention is to dispose the inlet mouth of such escape passage upon that surface of the relief unit which, during operation of the parts, trails, or faces away from the direction of rotation of the relief unit. Still further objects of the inventionv will appearas the description proceeds.

To the accomplishment of the above and related objects, my invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that change may be made in the specific construction illustrated and described, so long as the scope of the appended claims is not violated.

Fig. l is an elevation of the driving mechanism for a chainl saw, showing the gear housing in section, and embodying my invention;

Fig. 2 is an enlarged axial section through the output shaft of the gear train illustrated in Fig. 1, showing a relief unit associated therewith in accordance with my invention;

Fig. 3 is a transverse section taken substantially on the line 3-3 of Fig. 2; and

Fig. 4 is an end elevation of the relief unit.

While my invention, in its broad aspect, is, as indicated hereinabove, applicable to any lubricant-containing housing in which part-s are journalled for rotation, I have chosen to illustrate it in connection with a chain saw. In the drawings, the reference numeral I9 indicates generally the drive mechanism for such a saw including a housing II in which is mounted an electric motor whose spindle I5 projects into the interior of a gear housing I2 suitably associated with the housing II and formed to provide a chamber I3. A lling opening I4 is adapted to be closed by a suitable plug (not shown) and an output shaft I6 is suitably journalled in the housing I2, one end of said shaft projecting to the exterior of the housing. Within the chamber I3, a gear I'I is carried by the shaft I6 in mesh with .the toothed end of the spindle I5; and a sprocket I8 is carried on the projecting porti-on of the shaft I6 and secured in place by a nut IS threaded on said shaft projection. The sprocket I 8 is aligned with a. saw chain (not shown) carried upon a cutter bar 20 suitablysecured to the housing I2. All of this is standard construction,

The shaft I6 is hollow and, within the chamber I3, is formed With'a tapered and threaded radial port 22 communicating with the interior 2l of said shaft. A relief unit, indicated generally by the reference numeral 23, comprises a tubular housing 24 one end 25 of which is tapered and threaded for fluid-tight reception in the threaded port v22. A valve seat 2l is formed in said housing 24 near the inner end thereof to control flow between the interior 2I of the shaft I6 and the valve chamber 25; and a ball 28 is received in said chamber 26 and urged, by a spring 29, into sealing contact with the seat 21. The outer end o! the chamber 26 is closed by a plug 30 threadedly seated therein, a sealing wire 3| preferably being passed through registering openings in the valve housing 24 and the plug 30.

A passage 32 leads from the chamber 26 through the wall of the housing 24; and the mouth 33 of said passage opens through that face of the housing 24 which, during'lrotation of. the shaft IB, trails, or faces away from the direction of rotation.

When the parts are quiescent, the spring 29 willl hold the valve ball .28 in closing relation with-the valve seat 21; thus, no matter what position the unit I 3 may assume, fluid is prevented from ilow ing from the chamber I3 into the-interior 2l. off the shaft E6, and so to the atmosphere. When the unit is put into operation, they shaft IS will.1o. tate, at relatively high speed; and the effect of centrifugal force upon the ball 28 will overcome the effect of the spring-29, whereupon said ball will move offl its seat-to.=open communica-tiert between the chamber |31 and the atmosphere. through the passage 32'; past' the-seat'Zl, and throughthe bore 21|A ofthe shaft I6. Thusany tendency of" the rotating parts; to. buildi un a' fluid pressure' in the-chamber I3L'is overcome.

Because of the location and orientation ofthe passage 32, oil will never now from the chamber- I3 into the shaft bore 2|, since the valveZE; is never open except ati times when` the shaft |16:l is spinning at highr speed, andunder such circumstances, any oil in the passage 32. -or in thechamber 26 will be thrown, by centrifugall force, outwardly through thel passage 32: back:l into the chamber I3. There is verylittletendenoy'fon oil to enter the passage 32;*even beforefthe shaft attains a speed such as to-render centrifugal force eiective, vbecause the mouth 334 offsaidpassage is disposed in the trailing face ofl the-unit.

The saw is usually usedk either-in the position illustrated'inig. l, inV which the projectingend of the shaft I6 isV directed verticallyxdownwardln or in a position rotatedf'QO degrees. aboutftheaxis of the spindle I5, placing the shaft I-in awhoriz'm zontal position. The, oil level normally main1 tained in the chamber.' |3,;is j ustxbelow the; position of the unit 23; when the-assembly inthe illustrated attitude. When the' saw is used` with the shaft I in a horizontal p.ositionthe. unit?v 23 may splash into and' outi of theoil, at least. at the beginning and at the end of: operation; but loss of oil through the unit: 23sisxprevented; even under such circumstances, inthe manner-A above-described. As a matterof fact,.I'believe3 that, once the parts come to operating.- speed; the effect of the rotation of the gear: I'Tupon the; oil will be to holdzthe oilisubstantia'llydn anu an^ nular ring aroundV the outer rim of the chamber: E3, with the shaft lsubstantially dry;

I claim as my invention:

l. The combination with apower-transmission': gearing including a substantially.` iluidetighiz housing, a hollowV shaft'journalled'insaid housing and projecting therefrom, the interior of shaft opening tothe atmosphere; through the,- projecting portionv thereof; a.I second shaft' praz-- jecting into saidhousing, and-'gearingsoperatrvelyf connecting said shafts, ofV a pressurefrelief; tit,- ting comprising a valve housingf providingV a. chamber, said valve housing. being, carriedi on.: said hollow shaft' within I said fluid'fti'ghtzhousing; and projecting from said hollowshait'atanangler tothe axis of 'said hollow shaft, valvemeans con;- trolling communication between the interior. of;

sadhcll'owfshaft. and said'i chamber; andI meansf 75 resiliently tending to retain said valve means in condition closing such communication, said chamber being in open communication with the interior of said housing, whereby, when said valve means is in condition to open such communication, the interior of said housing is vented to the atmosphere.

2. The combination of claim 1 in which said valve means comprises a seat in said chamber adjacent said hollow shaft and a valve element engageable with said seat to close such communicationland movable away from the axis of said hollow shaft to open such communication.

3. The combination of claim 1 in which the communication between said chamber and the interior of' said' fluid-tight housing is through ai. port: in said. valve housing opening through that side of said valve housing which trails duringrotation of said hollow shaft.

4. In combination, a. substantially fluid-tight housing, a-.hollowzshazftz journalled in said housing and projecting therefrom, said' shaft beineT provided. within;v said; housing, with a substantia'lly radial. port, and: a. pressureY relier fitting seatedi in; and.' controlling. saidiport, said iitting comprising.v1 a, tubular" member projecting outwardly-fromzsaidshatz and providing; a chamber cmnmunicating atV one end, with the interior of saidshaitiandsopeningnear itsfother end to the interior; of; said; housing.H a= valvev4 seat near said. one end of=L said tting; a valve member coop` erablfrV with said:Y seat,l at. times, to prevent uid fl'ovm pasti said*v seat, andz spring means in. said: chamberF resiliently, urging saidrv valveV memberi toward saidroneendfoflsaid fittingrinto flow-pre venting: coopcnza-tion` with. said" seat,v the interior oi; said shaft being in opencommunication with atmosphere,

5..'Ihef combinationrof claim- 4'.- in. which saidY chamber 'opensfintof the'A interior of said housing.

through as port: whosezmouth is located on that surface off said: fitting.; whichtrails tion of'said-shaft;A

6r'. The. combination of4 claim 4 in whichA saidl ohamben'opens-:intotheiinterior off saidv housing,

ofi said fitting-.- whi'ch: trails: during.' rotation of.

said'lshaft.

8. Infcnmbination; a; substantially huid-tight housing; a; hollow, shaft, journalled.A in saidiahous ing.Y andiprojectingi therefrom, said shaft being: I provided-,xwithim said housing; with aylaterallyf opening porta=pressure relief ttingfcomprising'. as tubulan housing havingzan open endltted into saidA port; a; valve seat'finy saidtubular housing facing the` othery end? oi: said.l tubular housing a;

balli received'y in said tubular housing. and: cooperable.with said seat,` at times, to.' prevent fluid; flow'ftl'ierepast, andfa-spring in said tubular house` ingrbearing: upon saidfball and urging the same toward-saldi'seat, said'y tubularhousing being'pro-Y vided with?anfoutlettpassage opento the interior of:saidffluidetightfhousing.

9.: The: combination ofclaim 8- in: whiclr saidoutleta passage-- is; inclined; as it. leads from^- the interiolr'of. saidatubularr housing,.away from the axiszoisaidshaft:

outlet passage vopens thiough'thatfsurface of said tubular;housingv which. trailsduring. rotation ofsaidfishaft-u 11. The combination @claim-8 in.which.sad

during rotav and means is provided for retaining said plug lo against removal.

`CHARLES V. WOLFE.

6 REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,315,919 Fisher Sept. 9, 1919 1,882,716 Angle Oct. 18, 1932 1,978,835 Cotterman Oct. 30, 1984 

